In an email message, Solis says she submitted her resignation letter to President Barack Obama on Wednesday afternoon. She says she made the decision to leave after discussing it with her family and close friends.

Solis has won praise from labor unions for aggressive enforcement of wage and hour laws and job safety regulations. But business groups have criticized her as not taking a more cooperative approach.

A White House official says Attorney General Eric Holder and the secretaries of Health and Human Services and Veterans Affairs will remain with the Obama administration as it enters a second term.

The official said Holder, who leads the Justice Department, and HHS Secretary Kathleen Sebelius and VA Secretary Eric Shinseki will remain with the administration amid changes to the Cabinet as President Barack Obama moves into his second term.

The official, who spoke on condition of anonymity to discuss personnel changes, said the three remaining officials were not an exhaustive list of which Cabinet members intended to stay.

Obama has received some criticism that his initial Cabinet choices for the State Department and Defense Department do not reflect the nation's diversity.